When oil is squeezed between surfaces, like a bearing and a journal, VII polymers can align and stretch, causing a temporary drop in viscosity. Once past the bearing, the polymers return to their original shape, restoring viscosity. This temporary shear-thinning happens as the oil film thickness reduces temporarily under pressure but recovers once the stress
Tag Archives: VII
High stresses in engine areas such as the oil pump, camshaft, and piston rings can severely affect an oil’s viscosity, causing it to thin out and lose its load-carrying ability under high temperatures and shear forces, leading to engine wear. As shear rate increases, oil viscosity decreases. Multi-grade oils contain VII, which are large, flexible
VII come in various shapes, sizes, and quality levels, with larger molecules generally being better thickeners but more prone to breaking, affecting shear stability. Thickening Efficiency (TE) measures the increase in kinematic viscosity at 100°C after adding a specific amount of polymer. Higher TE indicates more effective thickening, influenced by polymer chemistry and molecular weight.